This invention relates to a single key preferential selection device in electronic musical instruments, and more particularly to the provision of a single key preferential selection device operated in a digital mode.
One example of a monophonic electronic musical instrument utilizing a single key preferential selection device is a monophonic music synthesizer as shown in FIG. 1.
The music synthesizer has a voltage controlled oscillator (VCO) 1 as a tone generator. The oscillation frequency thereof is varied in response to a tone pitch voltage KV which is an output from a key section 2 (including key switches and DC voltage sources) in correspondence to the tone pitch of a depressed key, so as to provide a tone source signal having the tone pitch of the depressed key. The output of the oscillator 1 is applied through a voltage controlled filter (VCF) 3 and a voltage controlled amplifier (VCA) 4 to a power amplifier 6 connected to a loudspeaker 5. Thus, the tone source signal is subjected to tone-coloring in the filter 3 and to envelope impartation in the amplifier 4 to provide a musical tone signal which is an output as a performance tone through the loudspeaker 5.
In this operation, control waveform signals ENVF and ENVA provided by control waveform generating circuits (E.G.) 7 and 8 are applied to the filter 3 and the amplifier 4, respectively, as a result of which the tone color and envelope of the musical tone signal are controlled according to the control waveform signals ENVF and ENVA, respectively. The control waveform generating circuits 7 and 8 operate to generate the control wave-form signals ENVF and ENVA the voltage values of which are varied with lapse of time in correspondence to a key-on detection signal which exhibits a step-up during the operation of a key in the key section 2. The shapes of the control waveform signals ENVF and ENVA are determined by control voltages CONF and CONA which are outputs by a control voltage generating circuit 9 operated by the performer.
The key section 2, in general, has a preferential selection circuit, so that even if a plurality of keys are operated, a tone pitch voltage signal KV corresponding to the key having the first priority order is outputed. Thus, the key section 2 has a function of selecting a single key for designating a single tone.
In all of the conventional key sections 2, signals are processed in an analog mode to conduct the preferential selection operation. Accordingly, the conventional key sections are not suitable for forming them in the form of an integrated circuit. Furthermore, for the same reason, miniaturization of the key section and simplification of the process of manufacturing the same are necessarily limited to a certain extent.